Surgeons frequently need to gain access to patients' body cavities to perform various procedures. One way to gain access to such a cavity is to perform invasive surgery where the cavity is opened fairly widely from the exterior to allow the surgeon ready access to the interior of the cavity. For example, in most traditional heart surgery, the patient's sternum is split and the overlying tissue is cut back to allow the surgeon to place both hands inside the chest cavity.
Increasingly, however, less invasive techniques are being employed to permit access to body cavities. For example, endoscopic examinations are being used to explore body cavities without having to directly visually inspect them. Gall bladder surgery is also being done increasingly by gaining access to the abdominal cavity through smaller access ports through the abdominal wall rather than using more invasive approaches. (See, for example, U.S. Pat. No. 5,375,588, issued to Yoon, the teachings of which are incorporated herein by reference.)
Increasingly, surgeons are gaining access to the thoracic cavity by passing surgical instruments into the cavity through the intercostal spaces between a patient's ribs. For example, U.S. Pat. No. 5,613,937 (Garrison et al., the teachings of which are incorporated herein by reference) suggests a method of conducting closed-chest heart surgery by passing surgical implements through a number of ports positioned in the intercostal spaces. This patent shows one access cannula which provides an oblong opening which allows a surgeon to pass a replacement valve into the thoracic cavity for placement in the patient's heart.
A wide variety of surgical retractors are also known in the art. Most surgical retractors are intended to allow a surgeon to forcibly urge tissue out of the way to enable unfettered access to the underlying anatomical structures. For example, U.S. Pat. No. 4,765,311 (Kulik et al., the teachings of which are incorporated herein by reference), shows a "wound retractor" which comprises a split tube. Each of the two tube halves are carried on holders which can be moved apart from one another to retract the tissue and provide access to the abdominal cavity. U.S. Pat. No. 1,157,202 (Bates) teaches a retractor which is used to retract the sides of an incision in the abdominal wall. This retractor includes four separate retractile elements which are arranged about an oval frame. The tissue can be pulled apart to expand the size of the opening of the incision by pulling the retractile elements away from one another.
U.S. Pat. No. 5,125,396 (Ray, the teachings of which are incorporated herein by reference), suggests a surgical retractor which comprises two separate arcuate blades. Each of these arcuate blades is carried by a separate ring. By turning these two rings with respect to one another, one can move the blades with respect to one another to open a generally cylindrical passageway through the patient's tissue.